Question

Find the no. of non negative integral solutions of: $x_1+x_2+x_3=15$.

• A. 15
• B. ¹⁵C₃
• C.
• D. ¹⁵C₂

Answer 1

The correct option is C

Non negative integral solutions means $x_1,x_2,x_3\ge 0$

This is also a "similar to different” type of question.

Applying 0's and 1's method:

Total no. of ways $=\frac{17!}{2!15!}.$ Hence option (c) is the correct answer.